This invention relates to a brewing (fermenting) tank of the closed type adapted to accelerate the brewing of materials to be brewed, such as soy, miso and a regenerative heater adapted for the brewing tank.
The breeding and metabolism of microorganism mainly produce in the brewing a product, such as soy or miso.
When the soy or miso is produced by means called "natural preparing or", a wooden fermenting or a concrete fermenting tank installed in a housing is utilized as a preparing vessel.
When the soy or miso is brewed in such a preparing vessel in a natural weather environment, it generally takes one year or longer to mature it.
However, the brewing of the soy or miso can be shortened in the maturing period while holding high quality by developing a low temperature preparing method, such as a technique for managing the temperature of the unrefined soy as a temperature brewing method, i.e., an unrefined soy temperature managing method for holding unrefined soy at suitable temperature for a predetermined period by preparing the unrefined soy at low temperature.
Ordinarily, an air conditioner is provided in a housing in which a preparing vessel is installed as temperature managing means in the unrefined soy temperature managing method as means for heating the whole housing. Since this means must manage the temperature in the whole housing, it has high facility cost and operation expenses.
To cope with this, it is proposed to build a tank of large capacity out of the housing by means of building material having excellent heat insulating property such as FRP, resin lining steel plates.
In brewing soy or miso using a large-sized brewing tank out of the housing as described above when applying the conventional unrefined soy temperature managing method, suitable heating means, such as a hot water circulating jacket or an electric heater is provided out of the brewing tank, and the heating means is covered with various heat insulating materials. Thus, the unrefined soy is heated with the heated means in the tank through the heating means in the brewing tank.
A waterproof heater is contained in the brewing tank as other heating means to directly heat the unrefined soy in the brewing tank through the heater.
In case of the brewing tank having the heating means at the periphery of the tank in the above-mentioned prior art, the outer wall of the tank is heated through the heating means, and the unrefined soy is heated in the tank by the thermal conduction of the heat from the outer wall. Heat does not readily arrive at the center of the tank by the heating means out of the tank, and the quantity of the heat dissipated from the heating means directly to the atmospheric air is not little. Thus, it is difficult to uniformly heat the unrefined soy in the tank and to suppress the loss of the thermal heat.
The above-mentioned drawbacks take place, particularly, when the brewing tank of outdoor installation type is increased in size due to the economy and mass productivity.
In the above-described prior art, in case of the heating means for containing the heater in the brewing tank, the unrefined soy in the tank can be directly heated by the heater, thereby eliminating mostly the thermal energy loss. But, the periphery of the heater becomes overheated and of ununiform temperature such that the temperature at the remote portion from the heater becomes insufficient and there is possibility that the useful microorganism of brewing dies by the overheat at the periphery of the heater.